Erasing Backgrounds and Other Large Areas

The Background Eraser tool is an intelligent (and really quite amazing) little feature. Not only does it remove the background from around very complex shapes, but it does so in a way that leaves a natural, softened, anti-aliased edge around the foreground object left behind. This technique would be impossible to pull off with the regular eraser tool, as it indiscriminately removes whatever pixels it touches. Because it erases pixels based on colors and tonal values that you control and modify, there is rarely much additional cleanup required once the background has been removed. Additionally, since the Background Eraser tool always erases to transparency, if you use it to remove the background from even a flattened layer, it automatically converts that layer to a floating, transparent one. This allows you to easily place a new background behind the foreground image, or to move it to a different image altogether.

To use the Background Eraser tool:

1.

Select the Background Eraser tool from beneath the Eraser tool in the toolbox (Figure 8.74).

Figure 8.74. The Background Eraser tool.

Alternatively, you can press E to select the Eraser tool and then press Shift+E to toggle to the Background Eraser tool.

2.

On the options bar, select a size using the brush Size slider.

3.

From the Limits pop-up menu, select one of the two limit modes (Figure 8.75).

Figure 8.75. The Limits pop-up menu controls which pixels beneath the brush are sampled and erased.

Contiguous mode erases any pixels within the brush area that are the same as those currently beneath the crosshairs, as long as they’re touching one another.

Discontiguous mode erases all pixels within the brush area that are the same as those beneath the crosshairs, even if they’re not touching one another.

Figure 8.76. You use the Tolerance slider to increase or decrease the number of pixels sampled based on their similarity to one another.

The Tolerance value controls which pixels are erased according to how similar they are to the pixels beneath the eraser crosshairs. Higher Tolerance values increase the range of colors that are erased, and lower values limit the range of colors erased.

5.

In the image window, position the eraser pointer on the edge where the background and foreground images meet and then drag along the edge.

The background portion of the image is erased, leaving behind the foreground image on a transparent background (Figure 8.77). Since the brush erases only pixels similar to the ones directly below the crosshairs, the entire background can be completely erased while leaving the foreground image intact.

Figure 8.77. Begin by placing the crosshairs of the brush in the background portion of the image (left), then drag the brush along the outside edge of the foreground object to erase the background (right). Continue around the edge of the foreground object until it’s completely separated from the background.